1. Field of the Disclosure
The disclosure relates to a reference frequency setting method, and more particularly, to a setting method that records a reference frequency into a memory, and a memory controller and a memory storage apparatus that use the method.
2. Description of Related Art
The universal serial bus (abbreviated USB hereinafter) device is already a very common and mature product in the commercial market. In order to generate a more accurate reference frequency for the operation of the electronic device, an external circuit is often used, that is, a crystal oscillator circuit. In the related art, if the property of the oscillator circuit in the chip needs to be adjusted, the manufacturer usually use a hardware component such as an e-fuse or a trim pad during the open-card process to record the adjustment setting. However, first, the crystal oscillator circuit is expensive, and second, recording the frequency setting of the oscillator circuit in the chip using the method necessarily adds to the hardware size and cost of the USB device. Moreover, after the card is opened, because the hardware component is already blown, the set frequency is hard to modify, which reduces the competitiveness thereof.
In general, the crystal-less oscillator usually requires tracking the frequency of a remote host to generate a more accurate reference frequency. However, under different test modes, the USB device that uses the crystal-less oscillator to generate a reference frequency may not have a frequency from a remote host to track. Therefore, when there is no frequency from a remote host to track, the reference frequency generated by the crystal-less oscillator may be less accurate, which causes the USB device to not be able to satisfy specific test specifications.
Nothing herein should be construed as an admission of knowledge in the prior art of any portion of the present invention. Furthermore, citation or identification of any document in this application is not an admission that such document is available as prior art to the present invention, or that any reference forms a part of the common general knowledge in the art.